In a method of operating an ink jet card printer, which includes a transport belt, a print unit including an ink jet print head, a sensor and a gantry, a card is loaded onto the transport belt along a processing axis using an exposed surface of the transport belt. The sensor and the ink jet print head are moved relative to the card using the gantry. A current position of the card is detected using the sensor. An image is printed to the card using the ink jet print head when the detected current position of the card indicates that the card is supported on the transport belt in a print position. Printing is interrupted when the detected current position of the card indicates that the card is not in the print position.